The Structure Gauging Train passes Narroways Hill Junction on 16 April 1991, with driving trailer RDB975081 leading. Multiple headlight fitted RDB975081 was formerly test coach Hermes, and started life as Mk 1 BSK coach M35313. The rear coach is RDB975280 (formerly test coach Mercury). This housed the computer equipment, and staff facilities. Between them is the structure gauging vehicle ZXQ DC460000. This odd looking contraption housed the optical gauging equipment. Providing the power at the rear on this occasion is 47974. Although there seem to be plenty of pictures of the later version of this train, I have been unable to find many pictures of this particular formation, especially on the move.